/*
 *
100
a1 size =  4
100
999

 */

#include <iostream>
using namespace std;
class A{
	public:
		int m_data;
		static int s_data;
		A(int data=0):m_data(data){}
};
int A::s_data = 100; //定义 并 初始化

int main(void){
	
	cout << A::s_data << endl;
	
	A a1(123);
	//不含有静态成员变量
	cout << "a1 size =  " << sizeof(a1) << endl;
	cout << a1.s_data << endl;
	
	A a2(1);
	a2.s_data  = 999;
	cout << a1.s_data << endl;
	return 0;
}
